An Exact Method for On-line Identification of FOPDT Processes

A new method for on-line process identification and PI controller tuning is proposed. The proposed structure inserts an ideal relay in parallel to a conventional PI controller to induce limit cycle output. The parallel connection of the ideal relay to the PI controller helps in designing a robust controller in presence of static load disturbances in the process. With the limit cycle measurement, a FOPDT transfer function model of the process dynamic is obtained. Based on the identified model, the controller is retuned to achieve good performance without disrupting the closed loop control. The performance of the proposed method is discussed by different simulation results to verify the effectiveness of the proposed method.